Programmable Completion Builtins (Bash Reference Manual)

8.7 Programmable Completion Builtins

Three builtin commands are available to manipulate the programmable completion facilities: one to specify how the arguments to a particular command are to be completed, and two to modify the completion as it is happening.

compgen

compgen [option] [word]

Generate possible completion matches for word according to the options, which may be any option accepted by the complete builtin with the exception of -p and -r, and write the matches to the standard output. When using the -F or -C options, the various shell variables set by the programmable completion facilities, while available, will not have useful values.

The matches will be generated in the same way as if the programmable completion code had generated them directly from a completion specification with the same flags. If word is specified, only those completions matching word will be displayed.

The return value is true unless an invalid option is supplied, or no matches were generated.

complete

complete [-abcdefgjksuv] [-o comp-option] [-DEI] [-A action] [-G globpat]
[-W wordlist] [-F function] [-C command] [-X filterpat]
[-P prefix] [-S suffix] name [name …]
complete -pr [-DEI] [name …]

Specify how arguments to each name should be completed. If the -p option is supplied, or if no options are supplied, existing completion specifications are printed in a way that allows them to be reused as input. The -r option removes a completion specification for each name, or, if no names are supplied, all completion specifications. The -D option indicates that other supplied options and actions should apply to the “default” command completion; that is, completion attempted on a command for which no completion has previously been defined. The -E option indicates that other supplied options and actions should apply to “empty” command completion; that is, completion attempted on a blank line. The -I option indicates that other supplied options and actions should apply to completion on the initial non-assignment word on the line, or after a command delimiter such as ‘;’ or ‘|’, which is usually command name completion. If multiple options are supplied, the -D option takes precedence over -E, and both take precedence over -I. If any of -D, -E, or -I are supplied, any other name arguments are ignored; these completions only apply to the case specified by the option.

The process of applying these completion specifications when word completion is attempted is described above (see Programmable Completion).

Other options, if specified, have the following meanings. The arguments to the -G, -W, and -X options (and, if necessary, the -P and -S options) should be quoted to protect them from expansion before the complete builtin is invoked.

-o comp-option

The comp-option controls several aspects of the compspec’s behavior beyond the simple generation of completions. comp-option may be one of:

bashdefault: Perform the rest of the default Bash completions if the compspec generates no matches.
default: Use Readline’s default filename completion if the compspec generates no matches.
dirnames: Perform directory name completion if the compspec generates no matches.
filenames: Tell Readline that the compspec generates filenames, so it can perform any filename-specific processing (like adding a slash to directory names, quoting special characters, or suppressing trailing spaces). This option is intended to be used with shell functions specified with -F.
noquote: Tell Readline not to quote the completed words if they are filenames (quoting filenames is the default).
nosort: Tell Readline not to sort the list of possible completions alphabetically.
nospace: Tell Readline not to append a space (the default) to words completed at the end of the line.
plusdirs: After any matches defined by the compspec are generated, directory name completion is attempted and any matches are added to the results of the other actions.

-A action

The action may be one of the following to generate a list of possible completions:

alias: Alias names. May also be specified as -a.
arrayvar: Array variable names.
binding: Readline key binding names (see Bindable Readline Commands).
builtin: Names of shell builtin commands. May also be specified as -b.
command: Command names. May also be specified as -c.
directory: Directory names. May also be specified as -d.
disabled: Names of disabled shell builtins.
enabled: Names of enabled shell builtins.
export: Names of exported shell variables. May also be specified as -e.
file: File names. May also be specified as -f.
function: Names of shell functions.
group: Group names. May also be specified as -g.
helptopic: Help topics as accepted by the help builtin (see Bash Builtins).
hostname: Hostnames, as taken from the file specified by the HOSTFILE shell variable (see Bash Variables).
job: Job names, if job control is active. May also be specified as -j.
keyword: Shell reserved words. May also be specified as -k.
running: Names of running jobs, if job control is active.
service: Service names. May also be specified as -s.
setopt: Valid arguments for the -o option to the set builtin (see The Set Builtin).
shopt: Shell option names as accepted by the shopt builtin (see Bash Builtins).
signal: Signal names.
stopped: Names of stopped jobs, if job control is active.
user: User names. May also be specified as -u.
variable: Names of all shell variables. May also be specified as -v.

-C command

command is executed in a subshell environment, and its output is used as the possible completions.

-F function

The shell function function is executed in the current shell environment. When it is executed, $1 is the name of the command whose arguments are being completed, $2 is the word being completed, and $3 is the word preceding the word being completed, as described above (see Programmable Completion). When it finishes, the possible completions are retrieved from the value of the COMPREPLY array variable.

-G globpat

The filename expansion pattern globpat is expanded to generate the possible completions.

-P prefix

prefix is added at the beginning of each possible completion after all other options have been applied.

-S suffix

suffix is appended to each possible completion after all other options have been applied.

-W wordlist

The wordlist is split using the characters in the IFS special variable as delimiters, and each resultant word is expanded. The possible completions are the members of the resultant list which match the word being completed.

-X filterpat

filterpat is a pattern as used for filename expansion. It is applied to the list of possible completions generated by the preceding options and arguments, and each completion matching filterpat is removed from the list. A leading ‘!’ in filterpat negates the pattern; in this case, any completion not matching filterpat is removed.

The return value is true unless an invalid option is supplied, an option other than -p or -r is supplied without a name argument, an attempt is made to remove a completion specification for a name for which no specification exists, or an error occurs adding a completion specification.

compopt

compopt [-o option] [-DEI] [+o option] [name]

Modify completion options for each name according to the options, or for the currently-executing completion if no names are supplied. If no options are given, display the completion options for each name or the current completion. The possible values of option are those valid for the complete builtin described above. The -D option indicates that other supplied options should apply to the “default” command completion; that is, completion attempted on a command for which no completion has previously been defined. The -E option indicates that other supplied options should apply to “empty” command completion; that is, completion attempted on a blank line. The -I option indicates that other supplied options should apply to completion on the initial non-assignment word on the line, or after a command delimiter such as ‘;’ or ‘|’, which is usually command name completion.

If multiple options are supplied, the -D option takes precedence over -E, and both take precedence over -I

The return value is true unless an invalid option is supplied, an attempt is made to modify the options for a name for which no completion specification exists, or an output error occurs.